Contents 3. Interaction Mechanics & Agency
How users act on systems and exercise control through interaction.
These determine whether interaction is physically, perceptually, and temporally efficient, and whether users feel in control.
Mission statement
Enable users to act on systems efficiently, predictably, and with a clear sense of control over their actions and outcomes.
Subcategories
1.Human-Interface ObjectsWhat users act upon.“Are all interactive objects in your system clearly defined, stable, and understandable?”8 directives2.AffordancesHow action is perceived.“Are possible actions in your system perceptually obvious to users at the moment of use?”9 directives3.Direct ManipulationHow action is executed.“Can users of your system act directly on visible objects with safe, reversible results?”9 directives4.FeedbackHow action is confirmed.“Does your system acknowledge users’ actions promptly and truthfully?”9 directives5.User EfficiencyWhy interaction quality matters.“Does your system measurably reduce users’ time and effort for real tasks?”9 directives6.Fitts’s LawThe governing physical constraint on all interaction.“Are frequent or critical targets in your system fast and easy to acquire physically?”10 directives7.InputHow users enter information.“Can users of your system enter information quickly and correctly the first time?”9 directives